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Author: Subject: Konrblum oxidation of 2-(chloromethyl)-2-methyl-1,3-dioxolane
finetune
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[*] posted on 9-10-2019 at 03:56
Konrblum oxidation of 2-(chloromethyl)-2-methyl-1,3-dioxolane


I want to try the Kornblum oxidation of 2-(chloromethyl)-2-methyl-1,3-dioxolane (CMD), CAS 4469-49-2, to 2-methyl-1,3-dioxane-2-carbaldehyde (MDC), CAS 39050-39-0.
Sadly, I did not find any data (mp, bp, density, etc) for MDC, can anybody please help me?
Any other procedure from the halogen to the aldehyde is highly appreciated.

CMD is prepared by the chlorination of acetone in ethylene glycol
J. org. chem. Vol. 46, 1981, 2532-2538 pdf

For the Kornblum I plan to dissolve CMD in excess DMSO, add equimolar triethylamine and reflux. Maybe NaHCO3 works aswell, I will have to try.

Thank you very much,
Finetune


CMD structure:

CMD.PNG - 3kB

MDC structure:



MDC.PNG - 3kB

[Edited on 9-10-2019 by finetune]
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[*] posted on 9-10-2019 at 05:44


Quote: Originally posted by finetune  
Any other procedure from the halogen to the aldehyde is highly appreciated.
https://en.wikipedia.org/wiki/Sommelet_reaction
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[*] posted on 9-10-2019 at 08:07


Thanks, but the acidic hydrolysis in the Sommelet may interferes with the ketal in CMD
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[*] posted on 13-10-2019 at 12:13


Ketals are actually quite resilient being bidentate. The sommelet reaction will give you an iminium cation which I would guess will react much more rapidly using a weak acid.
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[*] posted on 13-10-2019 at 12:41


Quote: Originally posted by Cactuar  
Ketals are actually quite resilient being bidentate. The sommelet reaction will give you an iminium cation which I would guess will react much more rapidly using a weak acid.

I agree, the sommelet reaction is just so easy.
Tried forming the adduct in ethanol from benzyl chloride and hexamine, but the intended delepine I had in mind hasn't happened afterwards when I used the adduct, I ended up with a very high yield of benzaldehyde instead of benzylamine.
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finetune
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[*] posted on 13-10-2019 at 15:41


Thanks!
After reading more about the ketals of (chloro-)acetone, it seems they are quite stable in dilute acid at RT. [J. Prakt. Chem. 156, 103-148 (1940), doi: 10.1002/prac.19401560402]

As I have hexamine on hand, I will try the Sommelet at first but it really depends on the yields.
The DMSO for the Kornblum is good 14 mol/L really cheap and the triethylamine is regeneratable (if one really needs TEA).
The hexamine is about 7.1mo/kg and more expensive.

I will post a synthesis of the chloroketal and the aldehyde anyway. Currently I am optimizing the conditions for the chloroketal synthesis from acetone and TCCA in ethylene glycol solvent.
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[*] posted on 14-10-2019 at 01:05


But keep in mind the kornblum oxidation stinks horribly.
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[*] posted on 16-10-2019 at 04:34


Yes, I thought about leading gaseous dimethylsulfate into a flame. H2O2 may work aswell, I will have to try.
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[*] posted on 16-10-2019 at 05:01


I used simply NaOCl bleach, the stuff from the supermarket with I think 3,8%.
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[*] posted on 16-10-2019 at 13:17


Thanks! Totally forgot about NaOCl!
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[*] posted on 17-10-2019 at 11:24


Some data on the aliphatic Sommelet:

https://pubs.rsc.org/-/content/articlelanding/1953/jr/jr9530...

It appears:

strong acid + low heat -> Delepine

weak acid + high heat -> Sommelet

but the latter is incompatible with enolizable aldehydes. Your aldehyde is not enolizeable -- I am not sure if the usual workup conditions (50% H2O/GAA, reflux) would destroy the ketal.

I should also mention, if triethylamine is available, triethylamine N-oxide can probably be used to prevent release of any DMS. The amine oxide acts as both base and oxidant and is more reactive than DMSO itself. See the attached paper (which uses trimethylamine N-oxide).

Attachment: godfrey1990.pdf (103kB)
This file has been downloaded 22 times





[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 19-10-2019 at 09:39


Thank you for the information, I will have a look into it.
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